For example, a clutch device, including a damper device, and a torque converter are provided between an engine and a transmission in an automobile. For reduction in fuel consumption, the torque converter is provided with a lock-up device for mechanically transmitting a torque at a predetermined rotational speed or greater.
Japan Laid-open Patent Application Publication No. 2018-013153 describes a lock-up device including a torque fluctuation inhibiting device. The torque fluctuation inhibiting device described in Japan Laid-open Patent Application Publication No. 2018-013153 includes an inertia ring, a plurality of centrifugal elements and a plurality of cam mechanisms. The inertia ring is rotatable relative to a hub flange to which a torque is transmitted, and a centrifugal force acts on each centrifugal element in rotation of the hub flange and the inertia ring. Each cam mechanism includes a cam provided on the surface of each centrifugal element and a cam follower making contact with the cam.
In the device described in Japan Laid-open Patent Application Publication No. 2018-013153, when the hub flange and the inertia ring are displaced in a rotational direction by torque fluctuations, each cam mechanism is actuated in response to the centrifugal force acting on each centrifugal element, and converts the centrifugal force acting on each centrifugal element into a circumferential force directed to reduce the displacement between the hub flange and the inertia ring. Torque fluctuations are inhibited by this circumferential force.
In the aforementioned device described in Japan Laid-open Patent Application Publication No. 2018-013153, as shown in FIG. 9, two right-side guide rollers and two left-side guide rollers, i.e., two pairs of guide rollers are disposed to stably move each centrifugal element in a radial direction.
In the torque fluctuation inhibiting device described in Japan Laid-open Patent Application Publication No. 2018-013153, the hub flange is provided with a plurality of recessed portions in the outer peripheral part thereof. The recessed portions are opened radially outward. The centrifugal elements are accommodated in the recessed portions, respectively, while being radially movable therein. In such a configuration, gaps are produced between the both circumferential lateral parts of each centrifugal element and sidewalls opposed thereto in each recessed portion. The gaps cannot be eliminated due to the structure of the torque fluctuation inhibiting device.
With the aforementioned gaps between each centrifugal element and each recessed portion, each centrifugal element tilts during actuation of the torque fluctuation inhibiting device. In accordance with the tilt of each centrifugal element, the profile of the cam provided on the outer peripheral surface of each centrifugal element is displaced from a designed profile, whereby a desired torsional characteristic (a characteristic indicating a relation between an angle at which the hub flange and the inertia ring are rotated relative to each other and a torque transmitted between the hub flange and the inertia ring) cannot be obtained. Additionally, the timing of tilt of each centrifugal element depends on the frequency of torque fluctuations. This results in a drawback of fluctuations in torsional characteristics.
In view of the above, when two pairs of guide rollers are provided as shown in FIG. 9 of Japan Laid-open Patent Application Publication No. 2018-013153, tilt of each centrifugal element can be inhibited to some extent. However, installation of the two pairs of guide rollers requires an attachment space radially enlarged as much as possible.